1. Field of the Invention
The present invention relates to a charge control agent (hereinafter referred to as a charge controller), and a toner binder composition and an electrophotographic toner containing thereof. More precisely, the present invention relates to a charge controller charging negatively, and a toner binder composition and an electrophotographic toner containing thereof.
2. Description of the Prior Art
Previously a charge controller for the purpose of controlling the electrostatic charge of an electrophotographic toner has been employed. As the charge controllers charging negatively among the charge controllers previously known, there have been known an azo dyestuff compound, a salicylic acid-metal complex and the like.
In these days, however, it is a problem from the safety viewpoint that these compounds contain such heavy metals as chromium, cobalt and zinc, and these compounds are originally colored ones (for example, azo dyestuff). In addition, another problem is that it is difficult to disperse these compounds finely in the toner, and therefore, the charge distribution becomes wide. As improved compounds, such polymer compounds are proposed as follows:
1) Copolymer of .alpha.-olefin and maleic anhydride (U.S. Pat. No. 4,442,189). PA1 2) Copolymer of styrene and maleic anhydride (Japan Patent Lay-open No.60-108861). PA1 1) at least a portion of said binder constitutes a continuous phase; PA1 2) at least a portion of the charge controller constitutes discontinuous domains; PA1 3) the charge controllers comprises a polymer moeity (.alpha.) forming the discontinuous domain, said moiety (.alpha.) having a solubility parameter same or lower by at most 2.5 than that of the continuous phase-forming binder (.beta.); PA1 4) said moiety (.alpha.) has an acid number of 50-400, and at least 3% of the acid group being a free acid group; PA1 5) the acid group-containing polymer is a polymer or copolymer comprising units of at least one acid group-containing monomer selected from the group consisting of a carboxylic acid group-containing monomer, a sulfonic acid group-containing monomer, a phosphoric acid group-containing monomer and a boric acid group-containing monomer; and PA1 6) said binder comprises at least one polymer selected from the group consisting of: a polymer or copolymer of at least one monomer selected from the group consisting of a styrenic monomer and an acrylic or methacrylic monomer; a polyester; an epoxy resin; a polyolefin; and a polyurethane. PA1 a polymer moiety (a) having an alkyl group containing 6-50 carbon atoms and a carboxyl group, said moiety (a) being selected from the group consisting of PA1 a polymer moiety (b), bound graft-wise or block-wise thereto, said moiety (b) being selected from the group consisting of PA1 (A1) a polymer or copolymer containing at least 5 mol. % of monomer units of PA1 (A2) a copolymer containing 5-75 mol. % of monomer units of PA1 further comprises a polymeric compatibilizer (.gamma.) having compatibility with both the polymer (A) and the toner binder. PA1 1) There is a continuous phase in at least a portion of the toner, PA1 2) There are discontinuous domains in at least a portion of the charge controller. PA1 (1) a monoalkyl ester of an .alpha., .beta.-ethylenically unsaturated dicarboxylic acid containing 6-50 carbon atoms in the alkyl group; and PA1 (2) a carboxylic group-containing .alpha., .beta.-ethylenically unsaturated monomer, and 6-80 mol. % of monomer units of PA1 (3) an ethylenically unsaturated monomer having an alkyl group containing 6-50 carbon atoms. PA1 1) a polymer (AA) having an alkyl group containing 6-50 carbon atoms and a carboxyl group and free from said moiety (b), said polymer (AA) being selected from the group consisting of said polymer (A1) and said polymer (A2); or PA1 2) a copolymer (AB) comprising: PA1 (B1) a styrenic polymer free from the moiety (a); and PA1 (B2) a polyester free from the moiety (a) can be contained in combination with (AB) and/or (AA).
3) Block copolymer of methyl methacrylate and methacrylic acid (U.S. Pat. No. 4,925,765).
By using the polymer compounds disclosed in 1) and 2), the problems of coloring and safety were solved. However, the dispersing property into the toner is poor and other properties, such as the electrostatic charge of the toner, the charging rate and the environmental stability, are also inadequate. Furthermore, as the transparency is poor when toner is formulated, a bad influence to the color tone is observed in applying the color toner.
The compound disclosed in 3) is the one which is intended to improve the dispersing property in addition to coloring and safety. However, the amount of the electrostatic charge of the toner and the charging rate are inadequate, as the charge controller is hardly exposed to the surface of the toner.
It is an object of the present invention to obtain an essentially colorless charge controller containing no metal.
Another object of the invention is to obtain a charge controller having excellent properties concerning the electrostatic charge of the toner, the charging rate and the environmental stability.
Still another object of the invention is to obtain a charge controller having no problem concerning the above-mentioned dispersing property and transparency.
These and other objects of the present invention will become more readily apparent from the description hereinafter.